In a current wireless communication system, miniaturization of a base station and densification of network nodes become an inevitable tendency in order to further improve the capacity of the network. However, the densification of the network nodes inevitably results in mutual interference between network nodes, and strong interference between nodes may greatly affect performance of the system.
In order to address an issue of interference between low power nodes, in 3rd Generation Partnership Project (3GPP), a lot of standardization efforts are made. In a scene of the R10/11 phase, in which a macro base station and a low power base station operate with a same frequency, a method of almost blank subframe (ABS) is introduced. In the ABS method, an interference resource may configure an ABS subframe in a subframe, an interfered node may schedule its user suffering severe interference in the ABS subframe. In the R12 phase, a method of switching on the small cell and switching off the small cell is introduced for a scene of denser small cells (a low power wireless access node, which may be understood as a micro cell base station). Some small cells may be turned on or turned off based on change of a service or change of the interference. In this way, interference between small cells can be avoided, and it is beneficial to save power for the base station.
In the case of introducing the method of switching on the small cell and switching off the small cell, the small cell needs to send a discovery reference signaling (DRS) when the small cell is in an off state, such that a terminal discovers and measures the cell. In the conventional mechanism, the terminal needs to maintain time and frequency synchronization continuously based on a pilot frequency sent by the base station. In addition, in order to reduce a transition delay between the on and off states of the cell, the terminal needs to measure and feed back channel state information (CSI) when the small cell is in the off state, such that the terminal can schedule the transmission performed by a user as quickly as possible when the small cell is in an on state.
Therefore, it is urgent to solve a technical issue of maintaining time and frequency synchronization of the terminal when the micro-cell base station is in the off state.